Tracking of saltating sand trajectories over a flat surface embedded in an atmospheric boundary layer

Abstract

Saltation is a major mechanism for the transport of soil particles. In the present study, we carried out wind tunnel tests to examine the saltating trajectories of two types of natural sand collected from a beach (diameter, d=300-500 mu m and 200-300 mu m respectively) as well as sand from the Taklimakan desert (d=100-125 mu m) in an atmospheric boundary layer. Consecutive images of saltating particles were recorded using a high-speed digital camera at a rate of 2000 fps with a spatial resolution of 1024 x 1024 pixels. The high temporal resolution of the acquired images enabled us to study the particle motion very close to the surface. The saltating particle trajectories were reconstructed from consecutive images, and the physical quantities characterizing the initial and final stages of the particle flight in the windward direction at friction velocities of about 10%-25% above the threshold friction velocity (u(*)/u(*t)=1.11-1.26) were analyzed statistically. In addition, the transverse deviation of the saltating particles from the main streamwise direction was evaluated. The results shed new light on the complicated motions involved in sand saltation and should prove useful in the evaluation and formulation of theoretical models. (c) 2006 Elsevier B.V. All rights reserved.